In vitro biological activities of silver nanoparticles using methanolic leaf extract of Plumeria rubra.

Plant phytochemicals play an immense role in the synthesis of metal nanoparticles, and the quality of phytochemicals used in the synthesis depends on the extraction method, solvent, temperature, etc. An extensive number of studies were carried out on the extraction of phytochemicals using aqueous extract during the synthesis of nanomaterials. Compared to distilled water, methanol can extract diverse phytochemicals at lower temperatures, and very few studies were done on this. Therefore, the present study aims to synthesize silver nanoparticles (AgNPs) using the methanolic extract of Plumeria rubra (PR) leaves. The successful synthesis of AgNPs was achieved by reducing Ag⁺ ions using PR extract. The phytochemistry of PR extract was observed using qualitative screening, Fourier transform infrared spectroscopy (FTIR), and gas chromatography with flame ionisation detection (GC-FID). The observed surface plasmon resonance using UV-visible spectroscopy confirmed the formation of PR-AgNPs, and the surface functionalization identified with FTIR correlated with the phytochemistry of the PR extract. X-ray diffraction and high-resolution transmission electron microscopy (HRTEM) methods revealed the amorphous nature and particle size distribution. Field emission scanning electron microscopy (FESEM) shows that PR-AgNPs particles have irregular shapes, some of which are embedded on sheet-like structures. The successful inhibition of V. parahaemolyticus was observed at lower concentrations among other tested organisms, and it also reduced 2,2'-diphenyl-1-picryl hydrazyl (DPPH). The hemocompatibility and in vitro cytotoxicity assays showed that PR-AgNPs had moderate activity. This study successfully synthesized AgNPs using PR extract, and its biological activities in vitro were also found to be effective.